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Model car

"a model car without context is more likely to be a scale model (a toy: google images for model car). Regarding the exercise guide, your native speaker has lied to you." – horatio

Playing a game.

"the person is a liar: "an exercise guide" makes perfect sense. Either the person who told you that lied about being a native speaker, or they are playing a game with you." – horatio

Two nouns in a row

"In grammar, genitive (abbreviated gen; also called the possessive case or second case) is the grammatical case that marks a noun as modifying another noun. It often marks a noun as being the possessor of another noun; however, it can also indicate various other relationships than possession: certain verbs may take arguments in the genitive case, and it may have adverbial uses (see Adverbial genitive)." -Wikipedia

First noun is modifying noun

"Placing the modifying noun in the genitive case is one way to indicate that two nouns are related in a genitive construction. Modern English typically does not morphologically mark nouns for a genitive case in order to indicate a genitive construction; instead, it uses either the 's clitic or a preposition (usually of). However, the personal pronouns do have distinct possessive forms. There are various other ways to indicate a genitive construction, as well. For example, many Afroasiatic languages place the head noun (rather than the modifying noun) in the construct state." -Wikipedia